docs: def cancel_subscription(self, sid):
          """
          Unsubscribes from a previously configured subscription.
          """
          url = urljoin(self._url_base, self._event_sub_url)
          headers = dict(
              HOST=urlparse(url).netloc,
              SID=sid
          )
          resp = requests.request('UNSUBSCRIBE', url, headers=headers, auth=self.device.http_auth)
          resp.raise_for_status()